A clean-shaven James Holmes appears in court in Centennial, Colorado in this September 2013 court sketch. (Bill Robles/Reuters)

CENTENNIAL, Colo. (Reuters) - Police coerced movie theater gunman James Holmes into talking about explosives found in his apartment after he shot 12 people to death, and those statements should be barred from his murder trial, defense lawyers argued in a Colorado courtroom on Monday.

Prosecutors stood by the admissibility of the statements, countering that police were merely trying to obtain information on how to safely defuse the bombs to protect law enforcement officers and the public from a potential detonation of the booby traps.

The latest legal back-and-forth in the high-profile case came in a hearing over what evidence should be allowed in the capital murder trial of the onetime neuroscience graduate student, due to start in early February.

Holmes, 25, is charged with first-degree murder and attempted murder for opening fire in a suburban Denver cinema during a midnight screening of the Batman film "The Dark Knight Rises" in July 2012.

The shooting rampage left 12 moviegoers dead and 70 others injured or wounded, some with permanent paralysis.

Holmes has pleaded not guilty by reason of insanity, and his lawyers have said their client was undergoing a psychotic episode when he sprayed the movie auditorium with gunfire before surrendering to police.

Prosecutors are seeking the death penalty for the California native if he is convicted.

Public defender Kristen Nelson said police denied Holmes' repeated requests to speak to a lawyer before he was questioned by investigators, and deceived him into thinking that the information he provided would not be used against him.

Had police allowed him to seek legal counsel immediately after his arrest, as required under the U.S. Constitution, a lawyer would have helped "protect this mentally ill man from being the instrument to his own conviction and execution," Nelson said.

Holmes, who has tended to stare straight ahead during courtroom testimony, bowed his head throughout Nelson's impassioned argument.

Prosecutor Rich Orman countered that police were unsure at the time if there was a second gunman at large and were dealing with a fluid situation.

"They could not know if setting foot in the apartment would trigger a massive conflagration," he said.

Defense lawyers also said the seizure of Holmes' bank accounts, which traced his firearms purchases, should be suppressed because there was not initially a valid, signed court order allowing the records to be released to prosecutors.

But prosecutors said they noticed what they called an oversight and informed the public defenders and the court of the error that was later rectified with a proper court order.

Arapahoe County District Judge Carlos Samour Jr. has not ruled on the suppression motions.